Induction-he ater



W. D. LUDWICK.

INDUCTION HEATER.

APPUCATION FILED APR. 24, I916- .1,193,404. Patented Aug. 1, 1916.

2 SHEETS-SHEET l- W. D. LUDWiCK.

INDUCTION HEATER.

APPLICATION FILED APR- 24, 1916.

1,193,404. Patented Aug. 1, 1916.

2 SHEETSSHEET 2.

&\\\\\ gllllllllll'l;VllllllIIIIIIIIIIIIIIIIII I UNITED STATES PATENT OFFICE.

WAYNE DOUGLAS LUDWICK, OF TACOMA, WASHINGTON, ASSIGNOR T0 ELECTRIC HEATING COMPANY, A CORPORATION OF WASHINGTON.

INDUCTION-HEATER;

To all whom it may concern:

Be it known that I, WAYNE DOUGLAS LUD- WICK, a citizen of the United States, and resident of Tacoma, in the county of Pierce and State of Washington, have invented certain new and useful Improvements in Induction-Heaters; and I do hereby cleclare the following to be a full, clear, and exact description of the same, reference being had to the accompanying drawings, forming part of this specification.

This invention relates generally to an induction heater of the type disclosed in my copending application filed October 21, 1914, Serial No. 867,820, and the primary object of the present improved construction is to attain an exceedingly high power factor in the heater combined with a maximum heating effect.

A further object of the invention is the provision of a novel system of heating water by induced magnetic hysteresis, eddy and secondary currents, in which the heating effect is under the control of the water in the system and the amount of heat generated in the heater may be reduced as the temperature of the water rises.

Other objects of the invention will ap pear from the ensuing detailed description, when taken in connection with the accompanying drawings which illustrate a structural embodiment of the invention in a preferred form.

The novel features of the invention will be particularly pointed out and specified in the claims at the end of the specification.

In the drawings :Figure 1 is an elevational sectional view of an induction heater constructed in accordance with the present improvements, the portion of the figure shown in section being taken in a plane indicated by the line 11 of Fig. 2. Fig. 2 is a transverse horizontal section of the improved heater taken in planes indicated by the line 22 of Fig. 1. Fig. 3 is a perspective view of a heater attached to a table for drying type matrices, with the electrical connections shown diagrammatically. Fig.

4 is an enlarged front elevation of a preferred form of thermostatic switch utilized for automatically controlling the heating of the water in the system.

Like characters of reference in the several figures indicate the same parts.

Specification of Letters Patent.

Patented Aug. 1, 1916.

Application filed April 24, 1916. Serial No. 93,223.

is substantially similar in all respects to the chamber at the top. In the present instance the heater is designed for heating water, and for this purpose, these chambers 7 are respectively adapted to be connected with the pipe lines of a water circulating system, by

means of screw-threaded sockets 8 leading out of the chambers. In this manner a flow of water may be maintained through the core 5. v

Surrounding the core 5 is a primary coil 10 consisting preferably of a plurality of windings of insulated conducting Wire. The coil 10 is adapted tobe connected with a suitable source of alternating current supply not herein illustrated, and is provided with three leads or terminal wires numbered respectively 12, 13, and 14. Lead. 12 is connected with the inner winding of the coil, lead 13 with the intermediate winding, and lead 14 with the outer winding. This permits a regulation of the amount of heat generated in the core 5, as will hereinafter more fully appear, since, if the leads 12 and 13 are placed in circuit, the current will traverse only the inner and intermediate windings of the coil, whereas, if the leads 12 and 14 are laced in circuit the current will traverse all the windings of the coil, thereby increasing the resistance and reducing the magnetic induction in the core 5. It will be understood that any desired number of leads and ing secured to the casing by screws 16. This prevents injury to the leads or terminal wires in handling the heater.

The magnetic circuit induced in the core by the alternating current passing through the coil 10 is completed from opposite ends of the coil through paths which are designed to reduce as far as possible magnetic resistance, hysteresis or the Foucault current in the return circuit. This is necessary in order to prevent great heat losses and to confine the heating effect essentially to the core 5. For this purpose, the return circuit is formed by laminated magnetic metal sections 17, preferably each substantially U- shaped and beveled at their upper ends to seat firmly within the undercut portion of 'the top casing plate 19, as shown more particularly in Fig. 1. The laminae or strips of the metal sections are respectively bound together by means of rivets 18, and the sections themselves are secured between the side casing plates 22 by the horizontal rods 28. The top and bottom casing plates 19, 20, are firmly secured to the said side casing plates by vertical rods 21. Vertical plates located between the ends of the side casing plates inclose the vertical portions of the laminated sections 17 from the outsi 1e. In the present instance, there are two laminated sections 17 facing each other with the horizontal portions of each section in contact with the core 5 above and below the coil 10. This provides a practically complete return for the magnetic circuit which is substantially without magnetic resistance, so that the magnetic hysteresis, secondary, and Foucault currents generated by the alternating cur- This chilling greatly increases the coercive' force of the metal of the core, and as the residual magnetism will also be increased, the hysteretic or heat producing factor will be correspondingly high. Theinvention also embodies the construction of the core of relatively low electric conducting properties, and partially of metal having relatively higher electric conducting properties. Embedded within the core and partially amalgamated therewith are pieces of material of high electric conducting properties. In the preferred form, these pieces consist of copper rings 9 entirely surrounded by the metal of the core. The effect of the ringsof high electric conducting material is to create short-circuited electric currents of low voltage but high amperage within the core, and as it is well known that currents of this kind have a very high heat producing factor, the heat generated by the magnetic hysteresis will be greatly enhanced. A core designed in accordance with the above description will be exceedingly eflicient because of the fact that the heatingis not dependent entirely upon the magnetic hysteresis, although this has been increased by chilling, thus increasing the coercive force of the core, but is supplemented by short circuited secondary currents having themselves a considerable heating effect.

The cavity 6 for the material to be heated is of a formation having a relatively small cross-sectional area in proportion to its walls, whereby the whole body of water flowing through the core5 is'brought into intimate contact with the metal of the core. As shown in Figs. 1 and 2 the cavity 6 is formed of a plurality of narrow flat channels extending longitudinally of the core 5 and set at angles to each other. In cross section the cavity or channel is shaped something like a cross, and it will be noted that a very considerable wall surface is provided although the cross-sectional area of the channel is very small. This serves to bring all of the liquid flowing through the core in very intimate contact with the metal of the core and greatly increases the capacity of the liquid to absorb the heat generated in the core.

In'Fig. 8 is illustrated a complete water heating system utilizing the present improved method of heating by magnetic hys-- teresis, secondary and Foucault currents, and in which provision is made for auto matic control of the heating of the water. As shown, the system is connected up with a table for drying type matrices, although it will be readily understood that the system may be applied to other uses as well. The

table 25 supports a chambered plate 26 to which the heater is connected by pipes 27 and 28, screwed into the screw-threaded openings 8 of the core 5, these pipes making provision for a continuous circulation of water throughthe core of the heater to the chambered plate 26 and back to the heater. A thermostat 29 is inserted through an opening into the chamber of plate 26. This partially of integral 'cast magnetizable metal thermostat is illustrated in its preferred embodiment in Fig. 4. As shown, it includes an expansible and contractible element orrod 30, which bears against a lever 31 pivoted at 32 within the casingof the thermostat. The lower end of said lever 31 bears against opposed screws 33 mounted on a second lever 34. The latter is pivoted at 35 to the casing and is impelled by a spring 36 in engagement withthe lever to make normally a contact with the contact screw 37, mounted on the right hand side of Fig. 4. A spring 39 is adapted to engage a projection on the lever 34, and retain the same in contact making position with screw 37. On the left hand side of the casing and opposite to screw 37 is a second contact screw 38, and at the lower end of the casing is a contact member 41 electrically connected with the spring 36. Spring 36 and lever 34 are formed of electric conducting material. Contact member 41 is connected with the line wire 42, and lead wire 12 of the heater is also connected with a line wire, as shown in Fig. 3; contacts 37 and 38 are respectively connected with the lead wires 13 and 14 of the heater. Normally the springs 36 and 39 maintain lever 34 in contact with contact screw 37, this placing wires 42, 13 and 12 in circuit. If the current is turned on it will pass only through the intermediate and in ner windings of the coil 10. IVhen, howeven-the water in the system is heated to the desired maximum temperature, rod 30 expands and moves lever 34 so as to disconnect contact member 37 and connect contact member 38. This operation places wires 42, 14 and 12 in circuit, and the current now flows through all of the windings of the coil thereby reducing the heat generated in the core and keeping the temperature down within the desired limits. If, for any reason, the temperature ofthe water falls below .lever 34 can be regulated, and this can be used to determine the amount of expansion of rod 30 necessary before shifting of the lever 34 from one contact member to another takes place.

The heated liquid, if the system is completely filled, will pass upwardly through pipe 27 and through plate 26, giving ofi' its heat, and returning through pipe 28 to the heater to be heated again. If the system is notcompletelyfilled, when the heat is suiiicient to vaporize the liquid in the heater, the vapor will pass into the chambered interior of the plate 26' and condense, returning as liquid through pipe 28 to'the heater.

What I claim is 1. In an electric heater, the combination of a core formed of integral cast magnetizable metal with a portion of the core chilled to increase the coercive force of the metal,

said core having a cavity therein for containing the material to be heated, a magnetizing coil surrounding the core, and a return for the magnetic circuit in contact with the core at opposite ends of the coil and having less magnetic resistance than the core.

2. In an electricheater, the combination oi a core formed of integral cast magnetizable metal with the outer surface of the core chilled to increase the coercive force of the metal, saidcore having a cavity therein for containing the material to be heated, a magnetizing coil surrounding the core, and a return for the magnetic circuit in contact with the core at opposite ends of the coil and having less magnetic resistance than the core. i

3. In an electric heater, the combination of a core formed of integral cast magnetizable metal with the outer surface of the core chilled to increase the coercive force of the metal, said core having a cavity therein for containing the material to be heated, a magnetizing coil surrounding the core, and a laminated return for the magnetic circuit in contact with the core at opposite ends of the coil.

4. Inan electric heater, the combination of a magnetic core of integral cast iron with the outer surface of the core chilled to increase the coercive force of the iron, said core having a cavity therein for containing the material to be heated, a magnetizing coil surrounding the core, and a return for the magnetic circuit in contact with the core at opposite ends of the coil and having less magnetic resistance than the core.

5. In an electric heater, the combination of a magnetic core formed partially of in- .tegral cast magnetizable metal but of relatively low electric conducting properties, and partially of metal having relatively higher electric conducting properties, said core having, a cavity therein for containing the material to be heated, a magnetizing coil surrounding the core, and a return for the magnetic circuit. in contact with the core at opposite ends of the coil and having less magnetic resistance than the core.

6. In an electric heater, the combination of a core formed partially of integral cast magnetizable metal, but of relatively low electric conducting properties and partially of metal having relatively higher electric conducting properties embedded in the mag netizable metal, said core having a cavity therein for containing the material to be heated, a magnetizing coil surrounding the core, and a return for the magnetic circuit in contact with'the core at opposite ends of the coil and having less magnetic resistance than the core.

' 7. In an electric heater, the combination of a core formed of integral cast magnetizable metal of relatively low electric conducting properties, a ring of metal of relatively higher electric conducting properties embedded in the metal of the core, said core having a cavity therein for containing the material to be heated, a magnetizing coil surrounding the core, and a return for the magnetic circuit in contact with the core at opposite ends of the coil and having less magnetic resistance than the core.

8. In an electric heater, thecombination of a core formed of integral cast magnetizable metal of relatively low electric conducting property, a ring of metal of relatively higher electric conducting properties embedded in and partially amalgamated with the metal of the core, said core having a cavity therein for containing the material to be heated, a magnetizing coil surrounding the core, and a return for the magnetic circuit in contact with the core at opposite ends of the coil and having less magnetic resistance than the core.

9. In an electric heater, the combination of a core formed of integral cast magnetizable metal of relatively low electric conducting properties, a copper ring embedded in and partially amalgamated with the metal of the core, said core having a cavity therein for containing the material to be heated, a magnetizing coil surrounding the core, and a return for the magnetic circuit in contact with the core at opposite ends of the coil and having less magnetic resistance than the core.

10. In an electric heater, the combination of a core formed of integral cast iron, a copper ring embedded in and partially amalgamated with the metal of the core, said core having a cavity therein for containing the material to be heated, a magnetizing coil surrounding the core, and a return for the magnetic circuit in contact with the core at opposite ends of the coil and having less magnetic resistance than the core. 1

11. In an electric heater, the combination of a core formed of integral cast iron partially chilled to increase the coercive force of the metal, a copper ring embedded in and partially amalgamated with the metal of the core, said core having a cavity therein for containing the material to be heated, a magnetizing coil surrounding the core, and a return for the magnetic circuit in contact with the core at opposite ends of the coil and having less magnetic resistance than the core.

12. In an electric heater, the combination of a core formed of integral cast iron with the outer surface of the core chilled to increase the coercive force of the metal, a cop.- per ring embedded in and partially amalgamated with the metal of the core, said core having a cavity therein for containing the material to be heated, a magnetizing coilsurrounding the core, and a return for the magnetic circuitin contact with the core at opposite ends of the coil and having less magnetic resistance than the core.

13. In an electric heater, the combination of a core formed of integral cast magnetizable metal, said core having a flat narrow channel therein for containing the material to be heated and of large wall surface in proportion to cross sectional area, a magnetizing coil surrounding the core, and a return for the magnetic circuit in contact with the core at opposite ends of the coil and having less magnetic resistance than the core.

14. In an electric heater, the combination of a core formed of integral cast magnetizable metal, said core having a plurality of communicating flat narrow channels therein of large wall surface in proportion to cross sectional area, the channels being adapted to contain the material to be heated, a magnetizing coil surrounding the core, and a return for the magnetic circuit in contact with the core at opposite ends of the coil and having less magnetic resistance than the core.

15. In an electric heater, the combination of a core formed of integral cast magnetizable metal, said core having a plurality of communicating flat narrow channels extending longitudinally of the core and set at angles to each other, the channels being adapted to contain the material to be heated, a magnetizing coil surrounding the core, and a return for the magnetic circuit in contact with the core at opposite ends of the coil and having less magnetic resistance than the core.

16. A core substantially for the purposes herein set forth, formed of integral cast magnetizable metal, and having the outer surface of the metal chilled, and a copper ring embedded in the core.

17. A core substantially for the purposes herein set forth, formed of integral cast magnetizable metal of relatively low electric conducting properties and having a ring of high conducting material embedded in the metal of the core.

18. A core substantially for the purposes herein set forth, formed of integral cast magnetizable metal of relatively low electric conducting properties and having a piece of high conducting material embedded in the metal of the core.

19. A core substantially for the purposes herein set forth formed of integral cast iron having its outer surface chilled to increase the coercive force of the iron, and apiece of high cor ducting material embedded in the metal of the core.

20. A core substantially for the purposes herein set forth formed of integral cast iron having its outer surface chilled to increase the coercive force of the iron, and a piece of cop er embedded inthe metal of the core.

21., core substantially for the purposes herein set forth formed of integral cast iron having its outer surface chilled to increase the coercive force of the iron and a ring of copper embedded in the metal of the core. A heating apparatus comprising, in combination, a core formed of magnetizable metal having a duct therein for the circulation of the medium to be heated, means for connecting said duct With a system from which the medium is supplied, an electric conductor surrounding the core in the form of a coil having a plurality of windings adapted to be connected with a source of alternating current supply, a return magnetic circuit in contact With the core above and below the coil and of form and material to prevent formation of eddy currents therein, and means responsive to a rise in temperature of the medium in the system for increasing the number of windings traversed by the current in the electric circuit,

23 A heating apparatus, comprising, in combination, a core formed oi magnetizahle metal having a duct therein for the circulation of the medium to be heated, means for connecting said duct "with a system from which the medium is supplied, an electric conductor surrounding the core in the form of a coil having a plurality of windings adapted to be connected With a source of alternating current supply, a return magnetic circuit in contact with the core above and below the coil and of form and material to prevent the formation of eddy currents therein, and a thermostatic switch responsive to a rise in temperature of the medium in the system for increasing the number of windings traversed by the current in the electric circuit.

WAYNE DOUGLAS LUDlVlCK. 

